Quick Answer:
Four 33¢ stamps and three 15¢ stamps equals $1.77 in postage.

Complete Solutions:
Several ways to do the problem:

Solution 1.
Using the hint on the first page, divide 177 by 33. With five 33¢ stamps, you have $1.65 worth of postage and need 12 more cents. With four 33¢ stamps, you have $1.32 worth of postage and need 45 more cents. Since three 15¢ stamps make 45¢, the solution is four 33¢ and three 15¢ stamps.

Solution 2.
Another strategy is to make a table (shown at left) listing all of the possible combinations of 33¢ and 15¢ stamps that can be used, without exceeding $1.77. Then work your way up, adding 15¢ stamps.

Solution 3.
Make a combination chart, (shown at right) and fill it out until you either reach or pass $1.77 in every row and column. The first row has the values of an increasing number of 33¢ stamps and the first column the values of increasing the number of 15¢ stamps. Remaining cells are the combinations of the two.

Solution 4. Another way to approach the problem is to realize that using only 15¢ stamps makes the total end in 0 or 5. Next look at the number of 33¢ stamps that can be used to make a total that ends in either 2 or 7.